Many weeds have reddish stems and rounded leaves as young seedlings, but the true leaves may have a different shape entirely. Purslane, on the other hand, has rounded leaves and red stems even when mature. To correctly identify weeds, consider the plant size, flowers and seeds, as well as leaf shape and colour.
Common purslane (Portulaca oleracea) is a succulent annual weed, with thick, fleshy leaves that taper slightly at the base. The leaves are glossy and rounded. Purslane spreads quickly and remains prostrate, rarely growing higher than 6 inches. It produces small yellow flowers in midsummer. The leaves are edible and are used in salads in some cultures.
Ladysthumb (Polygonum persicaria) and Pennsylvania smartweed (Polygonum pensylvanicum) are similar annual weeds. The first leaves are rounded, although true leaves are lanceolate, or spear-like. The stems are reddish and the leaves may have a purple watermark.
Redroot pigweed (Amaranthus retroflexus) is an annual weed that has red stems and rounded to oval leaves. It can grow 12 to 18 inches high. The petioles are tinged with red or purple.
Pull purslane by hand when the plant stands 4 to 6 inches high, but before it blooms. Weed when the soil is slightly moist, and make sure you get the entire root out. Do not leave purslane weeds laying on moist garden soil. It will re-root. Treat purslane with a glysophate herbicide while the plant is young or prevent purslane growth by applying a 3- to 4-inch layer of mulch.